Plotters and similar graphics equipment frequently utilize, pencils, pens and similar marking devices to develop a plot, graph or similar graphics. Typically, in an XY plotter, the paper, chart or other medium to be marked is moved back and forth through the plotter along the X-axis, and a carriage is moved perpendicular to the feed of the medium along the Y-axis. The carriage typically is adapted to receive a pen or similar marking device, and functions to move the pen back and forth along the Y-axis and to raise and lower the pen in order to develop the graphics picture in conjunction with movement of the paper along the X-axis.
Apparatus in plotters used to raise and lower marking devices should be simple in design in order to simplify repair and replacement of components. In addition, such apparatus should have low mass to allow rapid marker movement with little application of power. In general, apparatus used today to raise and lower marking devices is complex and constructed with many components. These components include synchronous belts, pulleys, and cams typically extending over the entire Y-axis of pen travel. It is difficult to repair such apparatus because this type of construction prevents easy access and removal of individual components. Furthermore, due to the high inertia of these components, they move comparatively slowly and require significant power to operate them. In addition, these parts are extremely noisy.